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 A302355 a(n) = coefficient of x^n in the n-th iteration (n-fold self-composition) of the g.f. of triangular numbers (A000217). 1
 1, 6, 72, 1390, 37515, 1307691, 56000728, 2847503268, 167737660533, 11236731677941, 843757483026150, 70200772129462767, 6410711453857626149, 637516967943664853331, 68581800216461580653064, 7935677122691714769565104, 982824624566131043920711329, 129722104862557293606783635718 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS N. J. A. Sloane, Transforms EXAMPLE The initial coefficients of successive iterations of g.f. A(x) = x/(1 - x)^3 are as follows: n = 1: 0, (1),  3,    6,    10,     15,  ... g.f. A(x) n = 2: 0,  1,  (6),  30,   137,    588,  ... g.f. A(A(x)) n = 3: 0,  1,   9,  (72),  543,   3933,  ... g.f. A(A(A(x))) n = 4: 0,  1,  12,  132, (1390), 14208,  ... g.f. A(A(A(A(x)))) n = 5: 0,  1,  15,  210,  2840, (37515), ... g.f. A(A(A(A(A(x))))) MATHEMATICA Table[SeriesCoefficient[Nest[Function[x, x/(1 - x)^3], x, n], {x, 0, n}], {n, 18}] CROSSREFS Cf. A000217, A030280, A119821, A302356. Sequence in context: A001763 A003235 A113133 * A089252 A052730 A010796 Adjacent sequences:  A302352 A302353 A302354 * A302356 A302357 A302358 KEYWORD nonn AUTHOR Ilya Gutkovskiy, Apr 06 2018 STATUS approved

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Last modified August 26 03:18 EDT 2019. Contains 326324 sequences. (Running on oeis4.)